Display module, electronic device, display module manufacturing method, and electronic device manufacturing method

Abstract

Provided is a display module with high light transmittance. A display module 10 according to one embodiment of the present invention comprises: a polyimide film 11; an image display structure 12 formed on the front surface of the polyimide film 11; and a reflection-suppressing uneven structure 13 formed on the rear side of at least a portion of the polyimide film 11.

Description

Display module, electronic device, method for manufacturing display module, and method for manufacturing electronic device

[0001] The present invention relates to a display module, an electronic device, a method for manufacturing a display module, and a method for manufacturing an electronic device.

[0002] Generally, display modules such as liquid crystal display modules and organic EL display modules are provided in electronic devices such as smartphones. In addition, electronic devices are generally provided with optical elements such as a camera that photographs a subject facing the display module and an environmental sensor that detects the intensity of light incident on the display module for adjusting the brightness of the display module. With the progress of miniaturization of electronic devices and enlargement of the display area of display modules, it has been studied to provide the display module and the optical element overlappingly in a plan view, that is, to provide the optical element on the back side of the display module (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 6-245209

[0004] Higher sensitivity of the optical element of the electronic device is also required. However, when the optical element is provided on the back side of the display module, there is a concern that the sensitivity of the optical element may decrease because the display module absorbs light. In view of such circumstances, an object of the present invention is to provide a display module having a high light transmittance and a method for manufacturing the same, and an electronic device in which the optical element disposed on the back side of the display module has high sensitivity and a method for manufacturing the same.

[0005] (1): A display module according to an aspect of the present invention includes a polyimide film, an image display structure formed on the surface of the polyimide film, and an antireflection uneven structure formed on the back side of at least a part of the polyimide film.

[0006] (2): In the display module of (1), the antireflection uneven structure may be a moth-eye structure.

[0007] (3) In the display modules of (1) to (2), the average period of the unevenness of the reflection-suppressing unevenness structure is 10 nm or more and 500 nm or less, and the average height of the unevenness of the reflection-suppressing unevenness structure may be 1.0 times or more and 20 times or less of the average period.

[0008] (4) In the display modules of (1) to (3), the reflection-suppressing uneven structure may be attached to the polyimide film.

[0009] (5) The display modules of (1) to (4) may further include a protective layer laminated on the back side of the polyimide film.

[0010] (6) In the display module of (5), the protective layer may have an opening that exposes the anti-reflection uneven structure.

[0011] (7) In the display modules of (1) to (6), the light transmittance of the polyimide film at a wavelength of 940 nm may be 90% or more.

[0012] (8) The display modules of (1) to (7) may further include a gas barrier layer laminated on the surface of the image display structure.

[0013] (9): An electronic device according to one aspect of the present invention comprises a display module (1) to (8), a sheet-like or plate-like cover member that covers the front side of the display module, and an optical element that is arranged on the back side of the reflection-suppressing uneven structure so as to face the reflection-suppressing uneven structure.

[0014] (10): In the electronic device of (9), the optical element may be either an image sensor or an optical sensor.

[0015] (11): A method for manufacturing a display module according to one aspect of the present invention comprises the steps of: forming a polyimide film by applying a polyimide precursor solution to the surface of a carrier substrate and heating it; forming an image display structure on the surface of the polyimide film; peeling the polyimide film on which the image display structure is formed from the carrier substrate; and arranging a reflection-suppressing uneven structure on at least a portion of the back surface of the peeled polyimide film.

[0016] (12): In the method for manufacturing a display module according to (11), in the step of arranging the reflection-suppressing uneven structure, a film having a moth-eye structure may be attached as the reflection-suppressing uneven structure.

[0017] (13): In the method for manufacturing a display module according to (11), in the step of arranging the reflection-suppressing uneven structure, the reflection-suppressing uneven structure may be formed by irradiating the back surface of the polyimide film with light or by contacting it with plasma.

[0018] (14): The display module manufacturing methods of (11) to (13) may further include a step of laminating a protective layer having an opening for exposing the reflection-suppressing uneven structure on the back side of the polyimide film.

[0019] (15): In the method for manufacturing a display module according to (14), in the step of laminating the protective layer, the protective layer having the opening formed in advance may be attached.

[0020] (16): In the method for manufacturing a display module according to (14), the step of laminating the protective layer may include the step of attaching a material sheet for forming the protective layer to the back side of the polyimide film, and the step of forming the opening in the material sheet attached to the back side of the polyimide film.

[0021] (17): In the method for manufacturing a display module according to (14), the step of arranging the reflection-suppressing uneven structure may be performed after the step of laminating the protective layer.

[0022] (18): An electronic device manufacturing method according to one aspect of the present invention comprises the steps of: manufacturing a display module by the display module manufacturing method described in (11) to (17); laminating a sheet-like or plate-like cover member on the front side of the image display structure; and arranging an optical element on the back side of the reflection-suppressing uneven structure of the display module so as to face the reflection-suppressing uneven structure.

[0023] According to the present invention, it is possible to provide a display module with high light transmittance and an electronic device with high sensitivity of optical elements disposed on the back side of the display module.

[0024] This is a cross-sectional view showing a partial configuration of an electronic device according to one embodiment of the present invention. This is a flowchart showing the procedure for a display module manufacturing method according to one embodiment of the present invention. This is a flowchart showing the procedure for an electronic device manufacturing method according to one embodiment of the present invention.

[0025] Embodiments of the present invention will be described below with reference to the drawings. Note that the dimensions of the various components in the drawings have been adjusted for ease of viewing.

[0026] [Electronic Device] Figure 1 is a cross-sectional view showing a partial configuration of an electronic device 1 according to one embodiment of the present invention. The electronic device 1 comprises a display module 10, a cover member 20, and a sensor module 30. The display module 10 of the electronic device 1 is itself an embodiment of the display module according to the present invention.

[0027] The display module 10 comprises a polyimide film 11, an image display structure 12 formed on the surface of the polyimide film 11, a reflection-suppressing uneven surface structure 13 formed on the back side of at least a portion of the polyimide film, a gas barrier layer 14 laminated on the surface of the image display structure 12, and a protective layer 15 laminated on the back side of the polyimide film 11.

[0028] The polyimide film 11 is a substrate on which the image display structure 12 is formed, that is, a base layer for the image display structure 12. Preferably, the polyimide film 11 has a light transmittance (JIS-K7375:2008) of 90% or more at a wavelength of 940 nm. The thickness of the polyimide film 11 is preferably 5 μm to 30 μm, and more preferably 8 μm to 20 μm, in order to achieve high light transmittance while providing sufficient strength when forming the image display structure 12 and the reflection suppression uneven structure 13. Furthermore, the polyimide film 11 may have an inorganic film (amorphous silicon, silicon oxide, silicon nitride, etc.) laminated on it, and multiple inorganic layers may be laminated on the polyimide film 11.

[0029] The image display structure 12 may be configured to display an image by individually emitting color from a large number of pixels arranged in a planar manner. As a specific example, the image display structure 12 may be an organic EL structure having a TFT array containing a large number of TFTs and a large number of organic light-emitting layers each driven by the TFTs.

[0030] The reflection-suppressing uneven surface structure 13 has numerous fine irregularities arranged substantially without gaps. The reflection-suppressing uneven surface structure 13 suppresses the reflection of light that is about to be emitted from the inside of the display module 10 to the outside on the back surface of the display module 10 by tilting the interface between the back surface of the display module 10 and the air using the fine irregularities. For this reason, the reflection-suppressing uneven surface structure 13 is arranged in at least the region facing the optical element 31, which will be described later, but it may also be arranged on the entire back surface of the polyimide film 11. As the reflection-suppressing uneven surface structure 13, a moth-eye structure with spindle-shaped protrusions is preferred, but it may also be a structure with pyramidal protrusions or depressions, or a structure with random irregularities. In this embodiment, the reflection-suppressing uneven surface structure 13 is arranged by attaching an uneven surface film 131, on which the reflection-suppressing uneven surface structure 13 has been formed in advance, to the back surface of the polyimide film 11 with an adhesive 132. The uneven surface film 131 can be formed from any transparent resin. As the adhesive 132, an optically transparent resin that is transparent and can prevent the formation of gaps between the polyimide film 11 and the textured film can be preferably used.

[0031] The average period of the surface irregularities of the reflection-suppressing surface irregularities 13 (average length ZSm of the contour curve elements, JIS-B0601:2013) is preferably 10 nm to 500 nm, and more preferably 50 nm to 300 nm, so as to suppress reflection across the entire visible light spectrum without making manufacturing excessively difficult. The average height of the surface irregularities of the reflection-suppressing surface irregularities 13 (arithmetic mean height Sa, JIS-B0601:2013) is preferably 1.0 to 20 times the average period, and more preferably 3 to 10 times, so as to enhance the reflection-suppressing effect without making manufacturing excessively difficult.

[0032] The gas barrier layer 14 covers the surface of the reflection-suppressing uneven structure 13, thereby preventing deterioration of the reflection-suppressing uneven structure 13 caused by contact with moisture, oxygen, etc. The gas barrier layer 14 can be formed from an inorganic film such as silicon oxide or silicon nitride. The thickness of the gas barrier layer 14 can be, for example, 100 nm to 500 nm.

[0033] The protective layer 15 is a material that ensures the strength of the display module 10, and in particular prevents excessive bending of the image display structure 12 before the display module 10 is incorporated into the electronic device 1. The protective layer 15 is formed from a film-like or sheet-like material with sufficient strength, and is typically formed from a resin sheet. The thickness of the protective layer 15 can be, for example, 30 μm or more and 50 μm or less. The protective layer 15 can be bonded to the back side of the polyimide film 11 or the anti-reflective uneven structure 13 with an adhesive 152. The protective layer 15 has an opening 151 that at least partially exposes the anti-reflective uneven structure 13. The opening 151 is an optical path through which light transmitted from the front to the back side of the display module 10 directly enters the sensor module 30. For this reason, the size and shape of the opening 151 are designed according to the sensor module 30.

[0034] The display module 10 having the above configuration has a reflection-suppressing uneven structure 13 on the back side of the polyimide film 11, which suppresses reflection at the interface with air when light incident from the front side is emitted to the back side, resulting in high light transmittance and high detection sensitivity of light that passes through the display module 10 to the sensor module 30 disposed on the back side.

[0035] The cover member 20 is formed from a transparent material having sheet-like or plate-like strength, and protects the display module 10 by covering its front surface. The material of the cover member 20 may include resin, glass, or a composite material of resin and glass. Preferably, the cover member 20 is bonded to the display module 10 without gaps using an optically transparent resin 21 to suppress reflection at the interface.

[0036] The sensor module 30 is disposed on the back side of the display module 10. The sensor module 30 has an optical element 31 facing the anti-reflection uneven structure 13, which is exposed through the opening 151 of the protective layer 15, on the back side of the anti-reflection uneven structure 13 of the display module 10. At least one of an image sensor such as a CMOS image sensor and an optical sensor such as an infrared sensor can be used as the optical element 31. The optical element 31 may be provided as part of a camera module. In other words, a camera module may be disposed on the back side of the anti-reflection uneven structure 13.

[0037] Thus, the electronic device 1 equipped with a display module 10 with high light transmittance has high sensitivity of the optical elements 31 as a whole.

[0038] [Manufacturing Method] The above-described display module 10 can be manufactured by the display module manufacturing method according to the present invention. The above-described electronic device 1 can also be manufactured by the electronic device manufacturing method according to the present invention.

[0039] Figure 2 is a flowchart showing the procedure of one embodiment of the display module manufacturing method according to the present invention. The display module manufacturing method according to this embodiment comprises a polyimide film formation step (step S01), an image display structure formation step (step S02), a gas barrier layer lamination step (step S03), a peeling step (step S04), a reflection suppression uneven structure arrangement step (step S05), and a protective layer lamination step (step S06).

[0040] In the polyimide film formation step S01, a polyimide film 11 is formed by coating a polyimide precursor solution onto the surface of a carrier substrate and heating it. As the carrier substrate, for example, a glass substrate, a metal plate, a polyethylene terephthalate film (PET film), etc., can be used, and a glass substrate is preferred from the viewpoint of heat resistance. When a glass substrate is used as the carrier substrate, alkali-free glass is preferred as the material of the glass substrate because it has relatively few movable ions. In addition, one or more coating layers selected from the group consisting of a silicon oxide layer, a silicon nitride layer, and an amorphous silicon layer may be formed on the surface of the glass substrate. Furthermore, a step of forming an inorganic film (amorphous silicon, silicon oxide, silicon nitride, etc.) on the polyimide film 11 may be included, and a step of forming multiple layers of the polyimide film 11 and the inorganic film may be included.

[0041] In step S02, the image display structure formation step, an image display structure 12 is formed on the surface of the polyimide film 11. The image display structure 12 can be formed by well-known methods such as printing technology, photolithography technology, or film formation technology.

[0042] In step S03, the gas barrier layer lamination process, a gas barrier layer is laminated onto the surface of the image display structure 12. The gas barrier layer can be laminated using a film deposition technique such as CVD.

[0043] In step S04, the peeling step, the polyimide film 11 on which the image display structure is formed is peeled off from the carrier substrate.

[0044] In the step of disposing the reflection suppressing uneven structure in step S05, the reflection suppressing uneven structure 13 is disposed on at least a part of the back surface of the peeled polyimide film 11. The disposition of the reflection suppressing uneven structure 13 may be performed by sticking an uneven film 131 having the reflection suppressing uneven structure 13 formed in advance to the back surface of the polyimide film 11. In this case, it is preferable to stick an uneven film 131 having a moth-eye structure as the reflection suppressing uneven structure 13. Further, the disposition of the reflection suppressing uneven structure 13 may be performed by forming the reflection suppressing uneven structure 13 from the material of the polyimide film 11 by processing the back surface of the polyimide film 11. The formation of the reflection suppressing uneven structure 13 can be performed, for example, by unevenly removing the material of the polyimide film 11 by irradiating light rays or contacting with plasma to the back surface of the polyimide film 11. Also, the reflection suppressing uneven structure 13 may be formed by embossing the back surface of the polyimide film 11.

[0045] In the step of laminating the protective layer in step S06, a protective layer 15 having an opening 151 for exposing the reflection suppressing uneven structure 13 is laminated on the back side of the polyimide film 11. The lamination of the protective layer 15 may be performed by sticking a protective layer 15 having the opening 151 formed in advance with an adhesive 152. Further, the lamination of the protective layer 15 may be performed by a method including a step of sticking a material sheet for forming the protective layer 15 to the back side of the polyimide film 11 and a step of forming the opening 151 in the material sheet stuck to the back side of the polyimide film 11. The formation of the opening 151 can be performed by laser ablation or the like.

[0046] The order of the step of disposing the reflection suppressing uneven structure in step S05 and the step of laminating the protective layer in step S06 may be interchanged. When the step of disposing the reflection suppressing uneven structure is performed after the step of laminating the protective layer, in the step of disposing the reflection suppressing uneven structure, the reflection suppressing uneven structure 13 will necessarily be formed only inside the opening 151.

[0047] FIG. 3 is a flowchart showing the steps of an embodiment of the method for manufacturing an electronic device according to the present invention. The method for manufacturing an electronic device according to this embodiment includes a display module manufacturing process (step S11), a cover member laminating process (step S12), and an optical element arranging process (step S13).

[0048] In the display module manufacturing process of step S11, the display module 10 is manufactured by the above-described display module manufacturing method.

[0049] In the cover member laminating process of step S12, a sheet-like or plate-like cover member 20 is laminated on the front side of the image display structure 12.

[0050] In the optical element arranging process of step S13, by arranging the sensor module 30 on the back side of the display module 10, an optical element is arranged on the back side of the reflection suppression uneven structure 13 so as to face the reflection suppression uneven structure 13.

[0051] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and various changes and modifications are possible. For example, in the display module according to the present invention, the gas barrier layer and the protective layer are not essential. Therefore, in the method for manufacturing a display module according to the present invention, the gas barrier layer laminating process and the protective layer laminating process can be omitted.

[0052] Hereinafter, examples of the present invention will be described. However, the scope of the present invention is not limited to the following examples.

[0053] <Fabrication of Display Module> [Example 1] 85.0 g of NMP (N-methylpyrrolidone) was added to a 300 mL glass separable flask equipped with a stirrer featuring a stainless steel stirring rod and a nitrogen inlet tube, and stirred as the organic solvent for polymerization. Next, while stirring the contents of the flask, 4.024 g of PDA (1,4-phenylenediamine) was added and dissolved. Then, 10.976 g of BPDA (3,3'-4,4'-biphenyltetracarboxylic dianhydride) was added to the contents of the flask, and the mixture was stirred at room temperature for 6 hours to obtain a homogeneous and transparent polyamic acid solution A. The obtained polyamic acid solution A was coated onto a glass substrate (Corning, product name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm x 100 mm) using a spin coater to achieve a film thickness of 10 μm after curing, and then pre-dried in a vacuum drying oven at 80°C and 100 kPa for 10 minutes. Subsequently, the oxygen concentration inside the furnace was adjusted to 20 ppm or less by creating a nitrogen atmosphere. The temperature was then raised from 23°C to 450°C at a heating rate of 5°C / min and held for 10 minutes to obtain a laminate in which glass and polyimide films were formed. Next, buffer layers made of silicon oxide (SiOx) and silicon nitride (SiNx) were laminated to a thickness of 1 μm using the CVD (Chemical Vapor Deposition) method. Then, an amorphous silicon (a-Si) layer was formed on the buffer layer using the CVD method, dehydrogenated annealing was performed at 450°C for 1 hour, and then an LTPS (Low Temperature Poly Silicone) layer was obtained by irradiation with an excimer laser. After that, a photosensitive acrylic resin was applied to the entire surface of the laminate, and exposure and development were performed using the photolithography method to form patterns on the LTPS layer. Next, an interlayer insulating film was formed, and then a gate electrode was formed by sputtering. After that, a photosensitive resin was applied, and exposure, development, and interlayer insulating film formation were repeated using photolithography to obtain a laminate with source / drain electrodes. A planarization layer was formed on this laminate, and an ITO film was formed on it by sputtering. After exposure and development using photolithography, pixel electrode patterning was performed.Next, PDL (Pixel Defined Layer) was applied, exposed, and developed to create a PDL pattern. A light-emitting layer was formed in each space partitioned by the PDL, and an upper electrode was formed to cover each space. Then, acrylic resin was alternately laminated using the CVD method, inkjet method, and UV irradiation, and a protective film was laminated to perform thin-film encapsulation. This laminate was then exposed to an excimer laser (wavelength 308 nm) from the glass substrate side at an energy density of 130 mJ / cm. ２ The laminate was irradiated with a 70% overlap condition, and the laminate and glass substrate were separated at the interface between the polyimide film and the glass substrate. A protective film with an opening was attached to the polyimide film side of the separated laminate. Next, a touch sensor, polarizing plate, and cover window were attached to the sealing layer side of the laminate, respectively. Then, a film with a moth-eye structure (Mosmite, manufactured by Mitsubishi Chemical) was attached to the polyimide film through the opening in the protective film as a reflection-suppressing uneven structure, and a display module with a reflection-suppressing uneven structure on the back side of the polyimide film was fabricated. An image sensor was installed as an optical element in the opening on the protective film side of this display module, and the imaging quality (sensitivity) of the image sensor was confirmed.

[0054] [Comparative Example] A display module was fabricated in the same manner as in Example 1, except that a film having a moth-eye structure was not attached to the polyimide film, and the imaging quality of the image sensor was confirmed.

[0055] <Method for measuring the light transmittance of polyimide film> [Example 1] Polyamic acid solution A from Example 1 was applied to a glass substrate (Corning Corporation, product name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm x 100 mm) using a spin coater, and fired at 120°C in air for 30 minutes and at 450°C in a nitrogen atmosphere for 10 minutes to obtain a polyimide film with a thickness of 10 μm. A moth-eye structure (Mitsubishi Chemical's Mosmite) was attached to the film, and the light transmittance at 300 to 1300 nm was measured using a JASCO UV-Vis-Near Infrared Spectrophotometer (V-650), and the transmittance at 940 nm was confirmed.

[0056] [Comparative Example 1] The transmittance at 940 nm for Comparative Example 1 was calculated using the same method as in Example 1, except that a film having a moth-eye structure was not attached.

[0057] The evaluation results for Example 1 and Comparative Example 1 are summarized in Table 1. As shown above, the display module equipped with a reflection-suppressing uneven structure that can increase light transmittance was able to improve the imaging quality of the optical element (image sensor).

[0058]

[0059] 1 Electronic device 10 Display module 11 Polyimide film 12 Image display structure 13 Reflection suppression uneven structure 131 Uneven film 132 Adhesive 14 Gas barrier layer 15 Protective layer 151 Opening 152 Adhesive 151 Opening 20 Cover member 21 Optical transparent resin 30 Sensor module 31 Optical element

Claims

1. A display module comprising: a polyimide film; an image display structure formed on the surface of the polyimide film; and a reflection-suppressing uneven surface structure formed on the back side of at least a portion of the polyimide film.

2. The display module according to claim 1, wherein the reflection-suppressing uneven structure is a moth-eye structure.

3. The display module according to claim 1 or 2, wherein the average period of the unevenness of the reflection-suppressing unevenness structure is 10 nm or more and 500 nm or less, and the average height of the unevenness of the reflection-suppressing unevenness structure is 1.0 times or more and 20 times or less the average period.

4. The display module according to claim 1 or 2, wherein the reflection-suppressing uneven structure is attached to the polyimide film.

5. The display module according to claim 1 or 2, further comprising a protective layer laminated on the back side of the polyimide film.

6. The display module according to claim 5, wherein the protective layer has an opening that exposes the reflection-suppressing uneven structure.

7. The display module according to claim 1 or 2, wherein the light transmittance of the polyimide film at a wavelength of 940 nm is 90% or more.

8. The display module according to claim 1 or 2, further comprising a gas barrier layer laminated on the surface of the image display structure.

9. An electronic device comprising: a display module according to claim 1 or 2; a sheet-like or plate-like cover member covering the front side of the display module; and an optical element disposed on the back side of the reflection-suppressing uneven structure so as to face the reflection-suppressing uneven structure.

10. The electronic device according to claim 9, wherein the optical element is either an image sensor or an optical sensor.

11. A method for manufacturing a display module, comprising the steps of: forming a polyimide film by coating a polyimide precursor solution onto the surface of a carrier substrate and heating it; forming an image display structure on the surface of the polyimide film; peeling the polyimide film on which the image display structure is formed from the carrier substrate; and arranging a reflection-suppressing uneven structure on at least a portion of the back surface of the peeled polyimide film.

12. The method for manufacturing a display module according to claim 11, wherein in the step of arranging the reflection-suppressing uneven structure, a film having a moth-eye structure is attached as the reflection-suppressing uneven structure.

13. The method for manufacturing a display module according to claim 11, wherein in the step of arranging the reflection-suppressing uneven structure, the reflection-suppressing uneven structure is formed by irradiating the back surface of the polyimide film with light or by contacting it with plasma.

14. The method for manufacturing a display module according to claim 11 or 12, further comprising the step of laminating a protective layer having an opening for exposing the reflection-suppressing uneven structure on the back side of the polyimide film.

15. The method for manufacturing a display module according to claim 14, wherein in the step of laminating the protective layer, the protective layer having the opening formed in advance is attached.

16. The method for manufacturing a display module according to claim 14, wherein the step of laminating the protective layer includes the steps of attaching a material sheet for forming the protective layer to the back side of the polyimide film, and forming the opening in the material sheet attached to the back side of the polyimide film.

17. The method for manufacturing a display module according to claim 14, wherein the step of arranging the reflection-suppressing uneven structure is performed after the step of laminating the protective layer.

18. A method for manufacturing an electronic device, comprising: a step of manufacturing a display module by the display module manufacturing method described in claim 11; a step of laminating a sheet-like or plate-like cover member on the front side of the image display structure; and a step of arranging an optical element on the back side of the reflection-suppressing uneven structure of the display module so as to face the reflection-suppressing uneven structure.

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